Recently, a controller area network (CAN) communication of a high speed and large capacity network and an electric power steering apparatus which realizes better steering stability, and function safety has been demanded.
An electronic apparatus in the electric power steering apparatus is strictly demanded to reduce noise to ensure the reliability of signals.
As a conventional noise suppression structure for suppressing noise, for example, the one illustrated in FIG. 14 is known (see PTL 1). FIG. 14 is a perspective view of a conventional example of a noise suppression structure.
A noise suppression structure 201 illustrated in FIG. 14 can change a noise suppression frequency by forming capacitance by two metal surfaces 202 and 203. The noise suppression structure 201 is disposed between a wireless circuit unit (not illustrated) and a digital circuit unit (not illustrated) so as to cut electromagnetic coupling between the wireless circuit unit and the digital circuit unit and prevent noise currents of both sides from flowing to each other.
The noise suppression structure 201 is formed on a ground layer 210 propagating noise, and the first metal surface 202 and the second metal surface 203 are placed on the same plane. A short circuit plate 204 is provided on an end part of the first metal surface 202, and the second metal surface 203 is provided with ground pins 205. The short circuit plate 204 and the ground pins 205 are connected to the ground layer 210.
The first metal surface 202 and the second metal surface 203 both have a comb-shaped pattern formed on a rectangular metal pattern. Each of the metal surfaces 202 and 203 are placed on the same layer and constituted in such a manner that the respective comb parts are arranged alternately so as not to contact with each other. The comb shapes are alternately implemented as described above, and thus a capacitor formed between the comb part of the first metal surface 202 and the comb part of the second metal surface 203 has a zigzag shape along the comb shape. The capacitor makes it possible to change a resonance frequency which enables noise suppression.